CODEWITHSUNDEEP
swift
krisacorn
krisacorn

Reputation: 831

Cannot increment a number in swift

I have a variable populated from a keystore, that when incremented, gives an error that reads: "NSNumber is not convertible to @lvalue UIint8"

if let bankbalance: AnyObject? = keystore.objectForKey("coinbalance"){
   let mybalance = bankbalance as NSNumber
    mybalance += 50 //this line gives the error 
}

My question is what is convertible to UIint8 so that I can add to my variable? I've tried INT, Float, double.

Upvotes: 2

Views: 3760

Answers (3)

Mitsuaki Ishimoto
Mitsuaki Ishimoto

Reputation: 3181

Use var. Because let means constants.

var mybalance = bankbalance as NSNumber

But NSNumber is a Object and mybalance.integerValue cannot be assigned.

if let bankbalance: AnyObject? = keystore.objectForKey("coinbalance"){
    let mybalance: NSNumber = bankbalance as NSNumber
    var b = mybalance.integerValue + 50;
}

Upvotes: 5

codester
codester

Reputation: 37189

You cannot increment constants.let is keyword in swift for constants which means after defining its value you cannot alter it. var is another keyword which means variable and you can alter the value which declared with var keyword.

if let bankbalance: AnyObject? = keystore.objectForKey("coinbalance"){

    //use var instead of let
    var mybalance = bankbalance as NSNumber
    mybalance = mybalance.integerValue + 50  //use integervalue as we cast to `NSNumber`
}

this will works

Upvotes: 3

Bas
Bas

Reputation: 4551

You are trying to add a value to a let and let is a constant, you can not assign values to a let after you initialized it.

Apple docs:

Constants and variables associate a name (such as maximumNumberOfLoginAttempts or welcomeMessage) with a value of a particular type (such as the number 10 or the string "Hello"). The value of a constant cannot be changed once it is set, whereas a variable can be set to a different value in the future.

var

is what you want

Upvotes: 8

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